The present application claims the benefit of priority from International Patent Application PCT/IB01/01631 filed on Sep. 5, 2001.
The present invention relates to a rotary tablet press comprising a housing, a rotary die table detachably connected to a drive shaft arranged in the housing for rotation of the die table, a number of dies arranged circumferentially in the die table, each die being associated with at least a first punch having a first end receivable in the die through an opening of the die and arranged for compression of a powder or granular material in the die by reciprocation of the punch, and at least a cam for cooperation with a second end of the punches in order to effect axial displacement of the punches by rotation of the die table, whereby a compression unit detachably mounted in the housing comprises the die table with punches, a feeding device for the supply of material to be compressed into the dies, and a tablet dish charge device for removal of compressed material in the form of tablets.
EP 0288 798 describes a tablet press having a die table rotatable about a vertical axis, each die having associated top and bottom punches receivable therein and the punches being guided by top and bottom cams, respectively, whereby the cams are stationary relative to the press housing. In order to facilitate change-over as well as cleaning of components between batches, the die table with punches and cams is detachable as a unit from the press housing.
EP 1 050 399 describes a rotary tablet press of the same type, in which the exchange of components between batches has been further improved by the provision of a U-shaped rigid connection frame between the top and bottom cams. The connection frame is detachably connected with the press housing, whereby the unit comprising connection frame, die table, punches and cams may be removed in a single operation by disconnection of the connection frame from the housing and disengagement of the die table from its drive shaft, Further, it is possible to fit auxiliary equipment, such as powder feeder and tablet outlet, on the connection frame, so that these components may be removed together with the unit.
Although these prior art tablet presses make it possible to replace a unit comprising the die table and more or less other components with a corresponding unit which has been cleaned in the meantime, it is still necessary to manually clean the remaining part of the press housing which surrounds the die table during production. During these cleaning operations, the production stands still. Further, the contaminated die table with associated components must subsequently be transported to a cleaning site, manually disassembled, cleaned and eventually assembled. During all these operations, the environment is contaminated with the product and the operator is exposed to the product. In addition, the operations are very time-consuming and therefore costly.
Moreover, by change-over between batches of toxic products, it is necessary to employ a so-called isolator or glove box built around the tablet press in order to prevent any contamination of the surroundings by the product. In this case, cleaning is much more difficult due to the limited accessibility and manoeuvrability in the glove box or isolator.
EP 0 637 507 describes a rotary tablet press provided with equipment for so-called washing-in-place (WIP) in the form of spray nozzles for spraying of washing agent onto the die table and associated components as well as suction pipes for draining off the washing agent. In known tablet presses of this type, it is, however, a problem that the washing by means of spray nozzles is not efficient enough to achieve the required final cleanliness due to the fact that the washing agent cannot adequately enter the complex construction of the die table with punches, the powder feeder and tablet outlet etc. Consequently, a time-consuming final manual cleaning of the tablet press is still necessary. The preceding washing-in-place operations by means of the spray nozzles also take long time, for instance up to eight hours, mainly due to long drying and cooling cycles after the wash cycle. During these cycles, the tablet press is out of production. In addition, the equipment required for washing-in-place comprises several spray nozzles and suction pipes, etc., and consequently increases the price of the tablet press considerably.
U.S. Pat. No. 4,259,049 describes a rotary tablet press in which some of the negative effects of dust generation have been alleviated during production. The leading end portions of the punches are surrounded by cuffs, through which gas is blown towards the front ends of the punches to prevent deposition of dust on the punch surfaces. In order to prevent the dust blown away from the punches from deposition on other components in the press housing during operation, said cuffs are surrounded by suction chambers provided by stationary mounted shields. However, due to these shields, change-over as well as cleaning of the machine between batches are even more complicated and consequently time-consuming, as the shields have to be removed manually to access the dies and associated punches. As this tablet press does not provide for removal of the die table and punches as a unit, these components must subsequently be disassembled also manually and one by one, all operations which are very time-consuming and must be done during stand-still of the machine.
The object of the present invention is to provide a tablet press by which the time required for cleaning of the press between batches is reduced compared to prior art presses and by which the risk of contamination of the surrounding environment as well as exposure of the operator to the product may be reduced to a minimum.
In view of this object, the compression unit encloses each die opening and its corresponding first punch end in a chamber, the feeding device and the tablet discharge device are enclosed, the feeding device communicates with an inlet for detachable connection with an external supply channel, and the tablet discharge device communicates with an outlet.
By enclosing both the area around the die where the tablets are compressed and the feeding and discharge devices, it is possible to keep the product always confined in the detachable compression unit, and the external supply channel, and by furthermore providing a releasable connection between the feeding device and the external supply channel, the compression unit may between batches fast and easily in a single operation be exchanged for an already cleaned unit, without having to clean supplementary parts of the tablet press, other than the supply channel, and without the operator being exposed to the product. Whereas the supply channel may be readily cleaned by means of well known techniques, such as cleaning-in-place (CIP) by means of spray nozzles, the compression unit requires a much more thorough cleaning procedure.
According to the invention, because the used compression unit confines the product residues, the unit may be transported to a dedicated cleaning station without contamination of the environment. The cleaning of the unit may be carried out manually, possibly in an isolator, without delaying the production, as another already cleaned unit is mounted in the tablet press for the production, but the cleaning may advantageously be automated. In a dedicated automated cleaning station, it is possible to clean the compression unit much more thoroughly and also faster than it is possible in the known tablet presses provided with washing-in-place equipment, because the unit is separated from its surroundings in the press, so that the operation of the cleaning equipment is not restricted by the limited space in the press. Further, the function of the tablet press is not affected by the presence of the cleaning equipment. As a result, the unit may be manipulated much more extensively by dedicated equipment, for example the punches may be moved vigorously in their dies during spraying with cleaning agent, the tablet feeder may be moved or even disassembled automatically, etc.
In addition, one automated cleaning station equipped with sophisticated manipulators and spray nozzles is able to serve several tablet presses which do only have to be out of production during a very reduced time for exchange of the compression unit between batches. As a result, in a production plant consisting of more tablet presses, the expenses of cleaning equipment are much reduced compared to tablet presses provided with cleaning-in-place equipment, because in the latter case, each press must be provided with expensive cleaning equipment.
In a preferred embodiment, the second punch ends are accessible for actuation from outside the compression unit. In this way, it is possible to accommodate actuation means, such as rollers and possibly the cams, in the press housing, whereby this equipment does not have to be replaced with the compression unit between batches, and furthermore it is possible to keep the actuation means outside the enclosed product area, so that the operation of this equipment is not negatively effected by the product particles, and so that the equipment does not have to be cleaned between batches. In addition, possible lubrication of the actuation means cannot result in contamination of the product with lubricants.
In a structurally particularly advantageous embodiment, the compression unit comprises a casing surrounding at least part of the die table, the feeding device and the tablet discharge device, and the inlet and the tablet outlet are arranged in a wall of the casing. By enclosing the compression unit by means of an integrated surrounding casing, cleaning of the unit in a dedicated cleaning station may furthermore be facilitated, the circulation of cleaning fluid in the casing may be optimised by appropriate design of the casing. In a cleaning station, supply and drainage of cleaning fluid may advantageously be conducted through the product inlet and the tablet outlet of the casing, respectively.
The casing of the compression unit may be provided with a releasable opening mechanism for opening of at least one door in the casing or detachment of at least a part of the casing from the compression unit in order to facilitate cleaning of the unit. The opening of the casing may advantageously be performed automatically in a closed chamber in an automatic cleaning station.
In an advantageous embodiment, each die is associated with first and second punches arranged for reciprocation in a direction parallel with the axis of rotation of the die table, the first and second punches are received in guides on either side of the die, respectively, said guides being accommodated in a rotary turret comprising the die table, the casing comprised by the compression unit surrounds the periphery of the turret and is sealed against the latter by means of seals permitting rotation of the turret in relation to the casing, and the casing has a bracket connected rotatably with the turret by means of a bearing. In this way, the second punch ends may project from opposed ends of the turret for actuation, and the compression area may be delimited by the periphery of the turret and the surrounding stationary casing. A tight sealing between the turret and the casing may be achieved as a result of the bearing centring the casing in relation to the turret.
The punches may advantageously be sealed against their guides at the first punch ends by means of seals permitting axial displacement of the punches in the guides, such as lip seals or bellows seals. This prevents product from entering the guide bores and thereby effecting the operation of the punches negatively.
In an advantageous embodiment, the compression unit has auxiliary devices communicating with the press housing via releasable connections, such as dust aspiration nozzles communicating with the press housing via releasable tube connections, a powder feeder driven through a releasable shaft connection by means of a drive accommodated in the tablet press housing, a lubrication system communicating with the press housing via releasable tube connections, etc. This allows optimising the function of the compression unit during production and at the same time ensuring fast and easy exchange of the compression unit. By the provision of dust aspiration nozzles, it is further possible to maintain an underpressure in the enclosure of the compression unit during production, thereby minimizing the risk of any leakage of the product. Even during exchange of the compression unit, an initial underpressure provided in the enclosure before separation of the unit from the press housing may provide additional safety against leakage.
In a preferred embodiment, releasable conduit connections between inlets or outlets of the compression unit and corresponding channels in the press housing are provided with a closure mechanism on either side of a disconnection mechanism. By closing the inlets or outlets in the compression unit and the corresponding channels in the press housing before releasing the connections, the enclosed product is still confined in the compression unit and the corresponding channels after disconnection of the unit from the housing, thereby preventing leakage of the product to the surroundings during exchange of the compression unit.
Advantageously, the releasable conduit connections are in the form of so-called double ball valves. In such a valve, a ball valve is provided on either side of a disconnection mechanism.
For use with toxic products, the releasable conduit connections are preferably in the form of so-called split valves having two mating valve members, such as split butterfly valves. This type of connection permits closing of the conduit passage and subsequently separation of the two valve parts, whereby each of the two mating valve members remains in its corresponding valve part closing the valve opening, practically without any leakage of the product to the surroundings.
Further, the releasable conduit connections may also be in the form of plastic tubes. This permits closing the connections by squeezing the plastic tube and heating it up, whereby it is welded together. The tube may then be cut through in the middle of the weld so that the two resulting tube ends are sealed.
In one embodiment, a number of top cams for cooperation with first punches and a number of bottom cams for cooperation with second punches are mounted on the compression unit for removal from the press housing together with the compression unit.
In another embodiment, a number of top cams for cooperation with first punches are mounted on the compression unit for removal from the press housing together with the compression unit, and a number of bottom cams for cooperation with second punches are mounted in the press housing so that the second punches are releasable from the bottom cams for removal from these together with the compression unit
Advantageously, a top cam for cooperation with punches is mounted adjustably on the compression unit. Thereby, in a cleaning station, it is possible to adjust the cam in order to move the punches in a way specifically suited for the cleaning operation, for instance they may be moved more vigorously by cleaning than by the tablet press operation.
In an advantageous embodiment, a compression roller for cooperation with first punches is supported above the compression unit by a height adjustable block, and the height adjustable block has a coupling element for engagement with a corresponding coupling element on the compression unit. In this way, two functions may be carried out by the height adjustable block; the correct height position of the compression roller during production may be set, and the die table of the compression unit may be lifted to disengage it from the drive shaft in the press housing in order to remove the compression unit for cleaning between batches.
In a further advantageous embodiment, the press housing is provided with a swivel arm pivotal about a vertical axis and provided with a coupling element for engagement with a corresponding coupling element on the compression unit. Thereby, the compression unit may after elevation from the drive shaft be swung out of the press housing and placed on a carriage for transfer to a cleaning station,
In an advantageous embodiment, the press housing is provided with a separate support for the feeding device, the feeding device is displaceable in relation to the compression unit, and said support has a snap coupling mechanism such as a pneumatic coupling mechanism for connection with the feeding device. The support provides for correct positioning of the feeding device in relation to the die table and the snap coupling mechanism ensures fast and easy disconnection of the feeding device from the support when the compression unit is to be removed.
The present invention also relates to a compression unit for releasable attachment in the housing of a rotary tablet press, the compression unit comprising a rotary die table for connection to a drive shaft arranged in the press housing for rotation of the die table, a number of dies arranged circumferentially in the die table, each die being associated with at least a first punch having a first end receivable in the die through an opening of the die and arranged for compression of a powder or granular material in the die by reciprocation of the punch, a feeding device for the supply of material to be compressed into the dies, and a tablet discharge device for removal of compressed material in the form of tablets,
According to the invention, the compression unit encloses each die opening and its corresponding first punch end in a chamber, the feeding device and the tablet discharge device are enclosed, the feeding device communicates with an inlet for detachable connection with an external supply channel, and the tablet discharge device communicates with an outlet.
In an advantageous embodiment, the compression unit comprises a casing surrounding at least part of the die table, the feeding device and the tablet discharge device, the inlet and a tablet outlet are arranged in a wall of the casing, and the casing of the compression unit is provided with a releasable opening mechanism for opening of at least one door in the casing or detachment of at least a part of the casing from the compression unit.
The invention further relates to a cleaning station for automated cleaning of a compression unit detached from a rotary tablet press, the compression unit comprising a number of dies arranged circumferentially in a rotary die table, each die being associated with at least a first punch having a first end receivable in the die through an opening of the die, a feeding device for the supply of material to be compressed into the dies, and a tablet discharge device for removal of compressed material in the form of tablets.
According to the invention, the cleaning station comprises at least two separate cleaning fluid devices each having a connection piece for detachable connection with a corresponding connection piece provided on the compression unit and communicating with an enclosure of the compression unit, the cleaning fluid devices being arranged for the supply of cleaning fluid to the compression unit and for the drainage of cleaning fluid from the compression unit. After connecting the connection pieces of the cleaning station with the corresponding connection pieces of the compression unit, possibly by means of snap connections, cleaning fluid may be circulated vigorously through the enclosure, possibly in alternating directions, thereby performing an effective cleaning of all components surrounded by the enclosure of the compression unit.
In an advantageous embodiment, at least one of the cleaning fluid devices is provided with a cleaning fluid spray nozzle arranged for automatic introduction through the corresponding connection piece on the compression unit. In this way, the cleaning fluid may be aimed more directly at the components to be cleaned, thereby ensuring a more effective cleaning.
The invention moreover relates to a cleaning station for automated cleaning of a compression unit detached from a rotary tablet press, the compression unit comprising a number of dies arranged circumferentially in a rotary die table, each die being associated with at least a first punch having a first end receivable in the die through an opening of the die, a feeding device for the supply of material to be compressed into the dies, and a tablet discharge device for removal of compressed material in the form of tablets, the cleaning station comprising a cleaning chamber for accommodation of the compression unit during cleaning, and the cleaning chamber being provided with at least a cleaning fluid spray nozzle, which cleaning station comprises an automatic manipulator for opening at least partially a chamber which is comprised by the compression unit and which before opening encloses at least a die opening and its corresponding first punch end. Thereby a very fast and effective cleaning operation is ensured, as the compression unit after placement in the cleaning chamber is cleaned automatically, and very good access to the components of the compression unit is obtained after opening the chamber comprising these components. The cleaning fluid may therefore be sprayed more directly at the components to be cleaned.
The cleaning chamber may be adapted so that the second punch ends are accessible for actuation from outside the cleaning chamber. This may be advantageous, if the second punch ends should be actuated during cleaning, but preferably kept out of contact with the cleaning fluid, thereby avoiding to relubricate these after replacement of the compression unit in the tablet press.
In an advantageous embodiment, the cleaning station comprises a drive shaft for detachable connection to the rotary die table of the compression unit for rotation of the die table during cleaning in order to effect axial displacement of the punches. This ensures effective removal of product particles trapped in the dies as well as particles sticking to the punches, especially around the sealings with their guides.
In a further advantageous embodiment, the cleaning station comprises an automatic manipulator for adjustment of a cam of the compression unit or the cleaning station comprises at least a cam for cooperation with a second end of the punches in order to effect axial displacement of the punches by rotation of the die table. By adjusting the cams of the compression unit or employing specially adapted cams of the cleaning unit, it is possible to move the punches in a way specifically suited for the cleaning operation, as exemplified above.
In a further advantageous embodiment, the cleaning station comprises an automatic manipulator for opening and/or moving a powder feeding device and/or a tablet discharge device of the compression unit. This ensures effective cleaning of the internal components of the powder feeding device and/or the tablet discharge device.
The invention additionally relates to a method of manufacturing tablets or the like in a rotary tablet press having a press housing and a compression unit comprising a number of dies arranged circumferentially in a rotary die table, each die being associated with at least a first punch having a first end receivable in the die through an opening of the die, a feeding device for the supply of material to be compressed into the dies, and a tablet discharge device for removal of compressed material in the form of tablets or the like, whereby the compression unit between batches of tablets is detached from the press housing and transferred to a cleaning station.
In the method according to the invention, during the pressing of tablets or the like and during the transfer of the compression unit to the cleaning station each die opening and its corresponding first punch end are maintained enclosed in a chamber of the compression unit and the feeding device and the tablet discharge device are maintained enclosed.
As a result of the above discussed more effective cleaning operation, which is hereby employed between the manufacturing of successive batches of tablets, the risk of contamination of a batch with product particles of a previous batch is minimized. Consequently, an even more pure end product may be obtained and therefore a product of higher quality. Further, because the need for cleaning of the press housing before insertion of a cleaned compression unit is eliminated, machine downtime is reduced, and production costs are reduced, resulting in a more competitive end product.
The invention further relates to a method of cleaning a compression unit detached from a rotary tablet press, the compression unit comprising a number of dies arranged circumferentially in a rotary die table, each die being associated with at least a first punch having a first end receivable in the die through an opening of the die, a feeding device for the supply of material to be compressed into the dies, and a tablet discharge device for removal of compressed material in the form of tablets, whereby at least one separate cleaning fluid device by means of a connection piece is connected with a corresponding connection piece provided on the compression unit and communicating with an enclosure of the compression unit, and subsequently cleaning fluid is supplied to the enclosure of the compression unit from the at least one cleaning fluid device. Preferably at least two cleaning fluid devices are employed, whereby cleaning fluid is drained from the enclosure to one of the cleaning fluid devices. The cleaning fluid may be circulated through the enclosure of the compression unit in alternating directions. Thereby the above-mentioned advantages are obtained.
The invention also relates to a method of cleaning a compression unit detached from a rotary tablet press, the compression unit comprising a number of dies arranged circumferentially in a rotary die table, each die being associated with at least a first punch having a first end receivable in the die through an opening of the die, a feeding device for the supply of material to be compressed into the dies, and a tablet discharge device for removal of compressed material in the form of tablets, whereby the compression unit is placed in a closed cleaning chamber, whereby, in the closed cleaning chamber, a chamber comprised by the compression unit and enclosing a die opening and its corresponding first punch end is opened, whereupon the compression unit is cleaned by means of cleaning fluid. Thereby the above-mentioned advantages are obtained.
In the closed cleaning chamber, the punches may be removed from the compression unit. This facilitates effective cleaning, as product trapped between the punches and their corresponding guides easier may be removed during cleaning.